1. Field of the Invention
This invention relates to lubricating oil compositions, their method of preparation, and use. More specifically, this invention relates to lubricating oil compositions which contain a molybdenum compound and an alkylated phenothiazine. The composition may further contain a secondary diarylamine. The use of both the molybdenum and the alkylated phenothiazine, and alternatively further with the secondary diarylamine, provides improved oxidation and deposit control to lubricating oil compositions. The lubricating oil compositions of this invention are particularly useful as crankcase and transmission lubricants.
2. Description of the Related Art
Lubricating oils as used in the internal combustion engines and transmissions of automobiles or trucks are subjected to a demanding environment during use. This environment results in the oil suffering oxidation which is catalyzed by the presence of impurities in the oil such as iron compounds and is also promoted by the elevated temperatures of the oil during use.
The oxidation of lubrication oils during use is usually controlled to some extent by the use of antioxidant additives which may extend the useful life of the lubricating oil, particularly by reducing or preventing unacceptable viscosity increases. Aminic antioxidants are antioxidants that contain one or more nitrogen atoms. An example of an aminic antioxidant is phenothiazine. The prior art discloses the many teachings on the synthesis and uses of phenothiazine. Phenothiazine antioxidants have been used as a stand alone additive, chemically modified or grafted onto the backbone of polymers.
Lubricant compositions containing various molybdenum compounds and aromatic amines have been used in lubricating oils. Such compositions include active sulfur or phosphorous as part of the molybdenum compound, use additional metallic additives, various amine additives which are different from those used in this invention, and/or have concentrations of molybdenum and amine which do not show the synergistic results obtained by this invention.
An interesting trend in the lubricant industry is a shift to lower and lower phosphorus levels. Thus, at some point the industry will require lubricant formulations for crankcase and transmission fluids, both automatic and manual, with zero or essentially zero phosphorus content.
Existing lubricants employing phenothiazine are taught in U.S. Pat. No. 5,614,124 and references cited therein, all of which are incorporated herein in their entirety by reference.
This invention relates to lubricating oil compositions, their method of preparation, and use. More specifically, this invention relates to lubricating oil compositions which contain a molybdenum compound and an alkylated phenothiazine. The composition may further contain a secondary diarylamine. The use of both the molybdenum and the alkylated phenothiazine, and alternatively further with the secondary diarylamine, provides improved oxidation and deposit control to lubricating oil compositions. The lubricating oil compositions of this invention are particularly useful as crankcase and transmission lubricants.
It has been found that the combination of (1) an oil soluble molybdenum compound and (2) an alkylated phenothiazine, and also preferably a secondary diarylamine, such as an alkylated diphenylamine, is highly effective at controlling crankcase lubricant oxidation and deposit formation. Examples of the types of compounds that may be used in this invention are described in the following. The alkylated diphenylamine (preferred secondary diarylamine) may be used at concentrations ranging from 0.1 to 2.5 wt. % in the finished lubricant, preferably between 0.2 to 1.5 wt. %. The molybdenum compound may be used between 20 and 1000 ppm, preferably between 20 to 200 ppm, based on the amount of molybdenum delivered to the finished lubricating oil. The alkylated phenothiazine may be used at concentrations ranging from 0.05 to 1.5 wt. % in the finished lubricant, preferably between 0.1 to 1.0 wt. %. In addition to the antioxidants of this invention, the lubricating composition may also contain dispersants, detergents, anti-wear additives including for example ZDDP, additional antioxidants if required, friction modifiers, corrosion inhibitors, anti-foaming additives, pour point depressants and viscosity index improvers. The lubricant may be prepared from any paraffinic, naphthenic, aromatic, or synthetic base oil, or mixtures thereof. In an embodiment, the lubricant may contain between 250 and 1000 ppm of phosphorus derived from ZDDP and between 500 and 3000 ppm of calcium from calcium containing sulfonate detergents or calcium containing phenate detergents. In this manner, both crankcase and automatic transmission fluid (ATF) lubricants are readily prepared.
Thus, in an embodiment of the present invention is provided crankcase and transmission fluid lubricants and additive package concentrates therefor, which contain very low levels of phosphorus. More preferred, are lubricant compositions containing zero or essentially zero phosphorus. By xe2x80x9cessentially zero phosphorusxe2x80x9d herein is meant phosphorus levels of less than or equal to about 100 ppm.
In another embodiment, the lubricant does not contain ZDDP, but may contain other sources of phosphorus.
I. Molybdenum Compounds
1. Sulfur- and Phosphorus-Free Organomolybdenum Compound
A sulfur- and phosphorus-free organomolybdenum compound that is a component of the present invention may be prepared by reacting a sulfur and phosphorus-free molybdenum source with an organic compound containing amino and/or alcohol groups. Examples of sulfur- and phosphorus-free molybdenum sources include molybdenum trioxide, ammonium molybdate, sodium molybdate and potassium molybdate. The amino groups may be monoamines, diamines, or polyamines. The alcohol groups may be mono-substituted alcohols, diols or bis-alcohols, or polyalcohols. As an example, the reaction of diamines with fatty oils produces a product containing both amino and alcohol groups that can react with the sulfur- and phosphorus-free molybdenum source.
Examples of sulfur- and phosphorus-free organomolybdenum compounds appearing in patents and patent applications which are fully incorporated herein by reference include the following:
1. Compounds prepared by reacting certain basic nitrogen compounds with a molybdenum source as defined in U.S. Pat. Nos. 4,259,195 and 4,261,843.
2. Compounds prepared by reacting a hydrocarbyl substituted hydroxy alkylated amine with a molybdenum source as defined in U.S. Pat. No. 4,164,473.
3. Compounds prepared by reacting a phenol aldehyde condensation product, a mono-alkylated alkylene diamine, and a molybdenum source as defined in U.S. Pat. No. 4,266,945.
4. Compounds prepared by reacting a fatty oil, diethanolamine, and a molybdenum source as defined in U.S. Pat. No. 4,889,647.
5. Compounds prepared by reacting a fatty oil or acid with 2-(2-aminoethyl)aminoethanol, and a molybdenum source as defined in U.S. Pat. No. 5,137,647.
6. Compounds prepared by reacting a secondary amine with a molybdenum source as defined in U.S. Pat. No. 4,692,256.
7. Compounds prepared by reacting a diol, diamino, or amino-alcohol compound with a molybdenum source as defined in U.S. Pat. No. 5,412,130.
8. Compounds prepared by reacting a fatty oil, mono-alkylated alkylene diamine, and a molybdenum source as defined in European Patent Application EP 1 136 496 A1.
9. Compounds prepared by reacting a fatty acid, mono-alkylated alkylene diamine, glycerides, and a molybdenum source as defined in European Patent Application EP 1 136 497 A1.
Examples of commercial sulfur- and phosphorus-free oil soluble molybdenum compounds are Sakura-Lube 700 from Asahi Denka Kogyo K. K., and Molyvan(copyright) 856B and Molyvan(copyright) 855 from R. T. Vanderbilt Company, Inc.
Molybdenum compounds prepared by reacting a fatty oil, diethanolamine, and a molybdenum source as defined in U.S. Pat. No. 4,889,647 are sometimes illustrated with the following structure, where R is a fatty alkyl chain, although the exact chemical composition of these materials is not fully known and may in fact be multi-component mixtures of several organomolybdenum compounds. 
II. Sulfur-Containing Organomolybdenum Compound
The sulfur-containing organomolybdenum compound useful in the present invention may be prepared by a variety of methods. One method involves reacting a sulfur and phosphorus-free molybdenum source with an amino group and one or more sulfur sources. Sulfur sources can include for example, but are not limited to, carbon disulfide, hydrogen sulfide, sodium sulfide and elemental sulfur. Alternatively, the sulfur-containing molybdenum compound may be prepared by reacting a sulfur-containing molybdenum source with an amino group or thiuram group and optionally a second sulfur source. Examples of sulfur- and phosphorus-free molybdenum sources include molybdenum trioxide, ammonium molybdate, sodium molybdate, potassium molybdate and molybdenum halides. The amino groups may be monoamines, diamines, or polyamines. As an example, the reaction of molybdenum trioxide with a secondary amine and carbon disulfide produces molybdenum dithiocarbamates. Alternatively, the reaction of (NH4)2Mo3S13*n(H2O) where n varies between 0 to 2, with a tetralkylthiuram disulfide, produces a trinuclear sulfur-containing molybdenum dithiocarbamate.
Examples of sulfur-containing organomolybdenum compounds appearing in patents and patent applications include the following:
1. Compounds prepared by reacting molybdenum trioxide with a secondary amine and carbon disulfide as defined in U.S. Pat. Nos. 3,509,051 and 3,356,702.
2. Compounds prepared by reacting a sulfur-free molybdenum source with a secondary amine, carbon disulfide, and an additional sulfur source as defined in U.S. Pat. No. 4,098,705.
3. Compounds prepared by reacting a molybdenum halide with a secondary amine and carbon disulfide as defined in U.S. Pat. No. 4,178,258.
4. Compounds prepared by reacting a molybdenum source with a basic nitrogen compound and a sulfur source as defined in U.S. Pat. Nos. 4,263,152, 4,265,773, 4,272,387, 4,285,822, 4,369,119, 4,395,343.
5. Compounds prepared by reacting ammonium tetrathiomolybdate with a basic nitrogen compound as defined in U.S. Pat. No. 4,283,295.
6. Compounds prepared by reacting an olefin, sulfur, an amine and a molybdenum source as defined in U.S. Pat. No. 4,362,633.
7. Compounds prepared by reacting ammonium tetrathiomolybdate with a basic nitrogen compound and an organic sulfur source as defined in U.S. Pat. No. 4,402,840.
8. Compounds prepared by reacting a phenolic compound, an amine and a molybdenum source with a sulfur source as defined in U.S. Pat. No. 4,466,901.
9. Compounds prepared by reacting a triglyceride, a basic nitrogen compound, a molybdenum source, and a sulfur source as defined in U.S. Pat. No. 4,765,918.
10. Compounds prepared by reacting alkali metal alkylthioxanthate salts with molybdenum halides as defined in U.S. Pat. No. 4,966,719.
11. Compounds prepared by reacting a tetralkylthiuram disulfide with molybdenum hexacarbonyl as defined in U.S. Pat. No. 4,978,464.
12. Compounds prepared by reacting an alkyl dixanthogen with molybdenum hexacarbonyl as defined in U.S. Pat. No. 4,990,271.
13. Compounds prepared by reacting alkali metal alkylxanthate salts with dimolybdenum tetra-acetate as defined in U.S. Pat. No. 4,995,996.
14. Compounds prepared by reacting (NH4)2 Mo3S13*2H2O with an alkali metal dialkyldithiocarbamate or tetralkyl thiuram disulfide as define in U.S. Pat. No. 6,232,276.
15. Compounds prepared by reacting an ester or acid with a diamine, a molybdenum source and carbon disulfide as defined in U.S. Pat. No. 6,103,674.
16. Compounds prepared by reacting an alkali metal dialkyldithiocarbamate with 3-chloropropionic acid, followed by molybdenum trioxide, as defined in U.S. Pat. No. 6,117,826.
Examples of commercial sulfur-containing oil soluble molybdenum compounds are Sakura-Lube 100, Sakura-Lube 155, Sakura-Lube 165, and Sakura-Lube 180 from Asahi Denka Kogyo K. K., Molyvan(copyright) A, Molyvan(copyright) 807 and Molyvan(copyright) 822 from R. T. Vanderbilt Company, and Naugalube MolyFM from Crompton Corporation.
Molybdenum dithiocarbamates are illustrated with the following structure, where R is an alkyl group containing 4 to 18 carbons or H, and X is O or S. 
II. Alkylated Phenothiazine
An alkylated phenothiazine suitable for this invention must be oil soluble or dispersible and correspond to the general formula below wherein R1 is a linear or branched C4-C24 alkyl, heteroalkyl or alkylaryl group and R2 is H or a linear or branched C4-C24 alkyl, heteroalkyl or alkylaryl group. 
Typical examples of alkylphenothiazine include but are not limited to monotetradecylphenothiazine, ditetradecylphenothiazine, monodecylphenothiazine, didecylphenothiazine monononylphenothiazine, dinonylphenothiazine, monoctylphenothiazine and dioctylphenothiazine.
General Preparation of an Alkylphenothiazine
Non-limiting examples of the preparation of alkylphenothiazine are mentioned in U.S. Pat. Nos. 5,614,124 and 2,781,318.
Diphenylamine can be alkylated with an olefin in the presence of a catalyst. Typical catalysts are acid clay or AlCl3. The alkyldiphenylamine can then be sulfurized in the presence of a sulfurizing agent and a catalyst. The preferred sulfur reagent and catalyst are elemental sulfur and iodine, respectively. Non-limiting other sulfurization catalysts are aluminum bromide, aluminum chloride, copper iodide, sulfur iodide, antimony chloride or Iron (III) chloride.
Thus, the alkyldiphenylamine can be of any structure so long as it contains at least one nitrogen atom, two aromatic rings such that each aromatic ring has at least one open ortho position to effect sulfurization and be oil soluble. A partial list of non-limiting alkyldiphenylamines suitable for sulfurization includes: monoctyldiphenylamine, dioctyldiphenylamine, monononyldiphenylamine, dinonyldiphenylamine, monodecyldiphenylamine, didecyldiphenylamine, monotetradecyldiphenylamine, ditetradecyldiphenylamine as well as various mixtures and combinations of these alkyldiphenylamines. Names of commercial alkyldiphenylamines suitable for use with this invention are Naugalube N-438L, manufactured by CK Witco, and Goodrite 3190NT, manufactured by Noveon.